A ritual is most effective if it incorporates symbols with positive meaning to the meditator. I previously shared symbols that can be used, and some meanings for each. There are deeper meanings in these symbols, but I believe that each meditator may find these meanings for themselves.
Most of us can not dedicate a whole room, but we can set aside smaller area in a room which can be used consistently for meditation. It is possible to include setting up your space in your opening ritual.
The reason for sitting is to keep the mind alert and avoid falling asleep. The table top holds the symbols you are using. It can also be used as a special area for reading and writing about spiritual growth. If you keep a pen and paper near, it is helpful to jot down your experience or question or comment and perhaps come back to the group and share it. We all learn from each other, we are all teachers and we are all students. I have not met anyone that I have not learned from.
The mirror represents the search for the truths which are within us all. It has been my experience that when I discover a truth, I know it immediately as there is no doubt in my mind as to it's veracity.
I use two candles as they represent the search for illumination as well as the element "fire". They are also plain white tapers, also for the symbolism, a personal choice. It would also be appropriate to carry a small candle, perhaps a lit tea lite into your meditation area and light your candles from it. They would form the points of a triangle. The number three and the triangle are meaningful in most of the worlds religions and philosophies.
The incense symbolizes thought floating upward and out into the Cosmos as well as the element "air". I use a stone burner to represent the element "earth" as well as my firm determination to seek spiritual growth.
The bowl of water represents the fourth element "water" and suggests nourishing my thirst for knowledge. It also nourishes the rose. As the rose opens in beauty with the shining of the sun, the soul blooms in the illumination I seek. When I can, I float a rose in the bowl of water, but if I do not have one, I simply devote some thought to the thirst for enlightenment and the slaking of this thirst with the water of life.